Exactly the same happened to me with the latest update. No items listed in Last session window and September history wiped out. Great. (only MX5 installed on my computer.) That Last session feature really makes me stay with Maxthon, but what's the point of it when it gets lost so easily?

This is how the History looks like. Obviously there is a big gap of few months. This is all now when they announced that History and Last Session could be imported from MX4. Who cares!!! Don't touch my data. Or at least make a backup of User folder to protect personal data and usage. I'm not the one who should think about it every time there is an update of YOUR browser.
Meanwhile, the new version can still be downloaded. Does anyone reads the forum here at all?
EDIT: So apparently, the MX4 data, which I stopped using but I did not uninstall it, got imported and overwritten, without even asking me. This messed up the MX5 History and Last Session.

When I've learned one thing at Maxthon the last few months: you have to store: history, bookmarks and search engines. Perhaps the snapshots are gone, but somehow sync again, then these are back. Yes, sync, anyway. That was different with MX4.

a skin - my own skin in MX5 - achieved by mods to the 3 dat files - as wilser and others post here - by blind updating you override these files for your own - users should have a choice as they may not have backups
in the same way the update overwrote files in the user dir - this resulted in my saved tabs being deleted - again something you should give choice on

not good enough - sorry - i run my own skin which involved mods to 3 dat files - you delete these to add your own - security or no security problem you should not ride roughshod overs users choice - that is not your function
if you have a problem then flag it with a notification or email to users - deleting a setup and modding a config file is not yours to do
like i said - keep the hell out of my system - even Microsoft give choice when it comes to updates - what makes you so special that you override users wishes

what have you changed - i have never had an auto update - this morning Maxthon had updated over night - i dont want that - i want to do it manually - you managed to delete some files i had in the maxthon main dir and modified the config file in users
NOT IMPRESSED
keep the hell out of my system - i will decide if i want to update - not you

Hey Maxers,
Welcome to having a try of the brand new release!
Version 5.1.2.2000
For the full release note and changelog: click here
Also available on Maxthon's official website
http://www.maxthon.com/
Happy browser and leave your comment!
Maxthon Team

Skynote is now Maxnote found by clicking your avatar at the upper left of the browser. If you are using an account your old contents should be displayed as well as synced to your android version if you use one.
You can create a new Maxnote by simply adding a new folder named Maxnote. In image I created Maxnote 2 as a demo